In current storage networks, and particularly storage networks including geographically remote access nodes and storage resources, preserving or reducing bandwidth between resources and access nodes is highly desirable as well as providing optimized data availability and access. Data access may be localized, in part to improve access speed to pages requested by host devices. Caching pages at access nodes provides localization, however, it is desirable that the cached data be kept coherent with respect to modifications at other access nodes that may be caching the same data. An example of a system for providing distributed cache coherence is described in U.S. Patent App. Pub. No. 2006/0031450 to Unrau et al., entitled “Systems and Methods for Providing Distributed Cache Coherency,” which is incorporated herein by reference. Other systems and techniques for managing and sharing storage array functions among multiple storage groups in a storage network are described, for example, in U.S. Pat. No. 7,266,706 to Brown et al. entitled “Methods and Systems for Implementing Shared Disk Array Management Functions,” which is incorporated herein by reference.
In an active/active storage system, if there are multiple interfaces to a storage device, each of the interfaces may provide equal access to the storage device. With active/active storage access, hosts in different locations may have simultaneous read/write access via respective interfaces to the same storage device. Various failures in an active/active system may adversely impact synchronization and hinder the ability of the system to recover. For example, in an active/active system in which a particular interface is preconfigured as, or otherwise biased to be, the principal interface or “winner” in the event of an network partition or node failure within a cluster of nodes, failure of that interface may result in data unavailability, data corruption and/or other problems. Other known solutions to active/active failure handling may include use of a quorum disk that resolves tie-break situations when a voting group of nodes disagree on the current state of a cluster. However, the use of physical quorum disks may be expensive to deploy and lack flexibility.
Accordingly, it would be desirable to provide an effective and efficient system to address issues like that noted above for a distributed storage system, particularly an active/active storage system.